1. Field of the Invention
This invention relates to a receiver drier which is used in a compact air-conditioning system, for example used in a vehicle, to temporarily store a liquid refrigerant.
2. Description of the Related Art
FIG. 1 is a plan view, showing a conventional receiver drier of the above described kind, and FIG. 2 is a front view of the receiver drier of FIG. 1, in FIG. 2 an upper end of the receiver drier being cut away along line II--II of FIG. 1.
As is shown in FIG. 2, the conventional receiver drier has a substantially cylindrical case 10 having an upper opening end and a closed lower end, and a cover member 14 fixed to the upper opening end of the case 10 by means of such as an arc welding and closing the upper opening end. In FIG. 2, reference numeral 12 denotes a welding portion between the upper opening end of the case 10 and the cover member 14. In an interior space of the case 10, a filter (not shown) for removing impurities in a liquid refrigerant, and a liquid refrigerant suction pipe 16 are contained. The suction pipe 16 extends through the filter along a longitudinal center line of the case 10 from a position near to the cover member 14, that is near to the upper end of the case 10, toward an inner portion of the case 10 so that it reaches a position near to a lower end of the inner space. In an outer surface of the cover member 14 which faces an outer space of the case 10, a liquid refrigerant outlet hole 18 is formed at a position located radially outwardly from a center of the cover member 14.
On an inner surface of the cover member 14 which faces the inner space of the case 10, a projection 19 is formed to extend from an upper end portion of the the suction pipe 16 to a position corresponding to an inner end portion of the refrigerant outlet hole 18. In the projection 19, a connecting passage 20 is arranged so as to communicate the upper end portion of the suction pipe 16 with the refrigerant outlet hole 18. An outer end portion of the refrigerant outlet hole 18 which is located in the outer surface of the cover member 14 functions as a discharge pipe connecting portion 21 to which a distal end of a liquid refrigerant discharge pipe (not shown) is connected. A liquid refrigerant observation hole 22 is branched from the liquid refrigerant outlet hole 18, and extends to a center of the outer surface of the cover member 14. An outwardly extending end of the observation hole 22 is sealed by a liquid refrigerant observation window 24. Further, in the cover member 14, a liquid refrigerant inlet hole 26 is formed at a position which is symmetrical with the discharge pipe connecting portion 21 of the liquid refrigerant outlet hole 18 with respect to the observation window 24. The liquid refrigerant inlet hole 26 extends through the cover member 14 from the outer surface thereof to the inner surface thereof, and an outer end portion of the inlet hole 26 which is located in the outer surface of the cover member 14 functions as an inlet pipe connecting portion 28 to which a distal end of a liquid refrigerant supply pipe (not shown) is connected.
Blind screw holes 34 and 36 are formed in positions of the outer surface of the cover member 14 in the vicinity of the discharge pipe connecting portion 20 and the inlet pipe connecting portion 28, respectively. These screw holes 34, 36 are used for fixing pipe pressing members 30 and 32 attached to the distal ends of the liquid refrigerant discharge pipe and the liquid refrigerant supply pipe, on the outer surface of the member 14 by means of fixing screws (not shown). Thus, the distal ends of the liquid refrigerant discharge pipe and the liquid refrigerant supply pipe are respectively pressed against the outer surface of the cover member 14 to communicate with the discharge pipe connecting portion 20 and the inlet pipe connecting portion 28 formed in the outer surface of the cover member 14, and are fixed thereon by means of the pipe pressing members 30 and 32 and the fixing screws.
FIG. 3 is a front view showing another type of conventional receiver drier, an upper end portion thereof being cut away. The receiver drier of FIG. 3 has the same basic structure as that shown in FIGS. 1 and 2, and hence elements similar to those shown in FIGS. 1 and 2 are denoted by corresponding reference numerals and no detailed explanation thereof will be given. The receiver drier of FIG. 3 differs from the receiver drier of FIGS. 1 and 2 only in that the former does not have the liquid refrigerant observation hole 22 and the liquid refrigerant observation window 24, and a liquid refrigerant outlet hole 18' is formed in the center of the outer surface of the cover member 14 so as to be concentric with the liquid refrigerant suction pipe 16. A projection 19' is formed in the center of the inner surface of the cover member 14 so as to be projected to the upper end portion of the liquid refrigerant suction pipe 16. In the projection 19', a connecting passage 20' is formed so as to extend in concentric with the liquid refrigerant suction hole 16 and to connect the upper end portion of the liquid refrigerant suction pipe 16 with the inner end portion of the liquid refrigerant outlet hole 18'. Thus, the discharge pipe connecting portion 21' of the liquid refrigerant outlet hole 18' is located in the center of the outer surface of the cover member 14. FIG. 3 shows a longitudinal section of the blind screw hole 34 which is not shown in FIG. 2. The other blind screw hole 36 has the same longitudinal section as that of the hole 34.
FIGS. 4A and 4B show longitudinal sections of two examples in which a distal end of the liquid refrigerant discharge pipe 38 is fixedly connected to the discharge pipe connecting portion 21' of FIG. 3 by means of the pipe pressing member 30 and the fixing screw. These two examples are also applicable to a case where a distal end of a liquid refrigerant inlet pipe (not shown) is fixedly connected to the inlet pipe connecting portion 28 by means of the pipe pressing member 32 (FIG. 1) and the fixing screw. Further, it is a matter of course that those two examples are applicable to the conventional case of FIGS. 1 and 2 where the ends of the liquid refrigerant discharge pipe and the liquid refrigerant supply pipe (not shown) are fixedly connected to the discharge pipe connecting portion 20 and the inlet pipe connecting portion 28 in the outer surface of the cover member 14 by means of the pipe pressing members 30 and 32 and the fixing screws, respectively. In the example of FIG. 4A, a headed bolt 40 is used, while in the example of FIG. 4B, a combination of a stud bolt 42 and a nut 44 is used.
Since the cover member 14 of the first conventional receiver drier shown in FIGS. 1 and 2 and the cover member 14 of the second conventional receiver drier shown in FIGS. 3, 4A and 4B are obtained by cutting a round bar or a substantially disk-shaped blank which is formed by forging, the cover member 14 is thick and heavy. Further, it is difficult to appropriately and constantly satisfy a welding condition required to fix the thick, large and heavy cover member 14 which has a large thermal capacity, to the opening end of a thin peripheral wall of the case 10 in an airtight manner by welding. Therefore, a relatively great amount of time is necessary for welding.